1. Field of the Invention
The present invention generally relates to an electronic auxiliary lighting system for a high intensity discharge lamp.
2. Description of Related Art
Generally, high-intensity discharge (xe2x80x9cHIDxe2x80x9d) lamps will extinguish when power to the HID lamp is interrupted. Power interruptions of even a very short duration, e.g. milliseconds, will often extinguish the HID lamp. As is well known in the art, generally, an extinguished HID lamp will not immediately re-ignite upon the restoration of power to the HID lamp because gases within the HID lamp must be cooled before the HID lamp will re-ignite. Furthermore, when the HID lamp is re-ignited, its lumen output is usually only a fraction of the normal lumen output and gradually increases until the HID lamp is at full brightness. Typically, it may take several minutes after restoration of power to the HID lamp before the HID lamp actually attains full brightness. Accordingly, auxiliary lighting control circuitry has been used for automatically lighting an auxiliary light source, such as an incandescent lamp, following a brief power interruption of an HID lamp.
Many standard magnetic HID ballasts provide an auxiliary tap to power an auxiliary light source if the HID lamp extinguishes. The auxiliary light source is controlled by the auxiliary lighting control circuitry that is external to the ballast. Typically, the primary winding of a current transformer is connected in series with the HID lamp. The auxiliary lighting control circuitry senses the ON/OFF condition of the HID lamp by sensing the HID lamp current available at the auxiliary tap. During normal operation of such an auxiliary lighting system, the HID lamp is ON (i.e. energized) and the auxiliary light source is OFF (i.e. de-energized). However, such external auxiliary lighting control circuitry increases the per-unit cost of the HID ballast system. Furthermore, external circuitry may cause additional problems pertaining to packaging and limited available space.
What is needed is an auxiliary lamp system that does not require an auxiliary tap or external circuitry.
The present invention is directed to, in one aspect, an auxiliary lighting system for a HID lamp, comprising an auxiliary light source, a switch circuit for controlling the application of a voltage source to the auxiliary light source, the switch circuit having a first state that effects application of the voltage source to the auxiliary light source, and a second state that isolates the voltage source from the auxiliary light source, and a control circuit having an input for receiving and being responsive to a signal that indicates the operational state of a HID lamp, the control circuit controlling the duration of time in which the switch circuit is configured in the first state and in the second state wherein the duration of time depends upon the operational state of the HID lamp.
In a related aspect, the present invention is directed to a method of operating an auxiliary lighting system for use with a HID lamp, comprising the steps of providing an auxiliary lighting system comprising an auxiliary light source, and a switch circuit having a first state for effecting application of a voltage source to the auxiliary light source and a second state for isolating the voltage source from the auxiliary light source, providing a status signal that indicates the state of energization of a HID lamp, and controlling the duration of time in which the switch circuit is configured in the first state and the second state wherein the duration of time depends upon the state of energization of the HID lamp.
In another aspect, the present invention is directed to an auxiliary lighting system for a high-intensity discharge lamp. The auxiliary lighting system has an auxiliary light source, an HID lamp status circuit having an input for connection to a status signal representative of the operational state of a high-intensity discharge lamp wherein the HID lamp status circuit determines whether the status signal meets predetermined signal criteria, a switch circuit for controlling the application of a voltage source to the auxiliary light source wherein the switch circuit has a first state that effects application of the voltage source to the auxiliary light source, and a second state that isolates the voltage source from the auxiliary light source, and a control circuit responsive to the HID lamp status circuit for controlling the switch circuit. The control circuit has a first state when the HID lamp status circuit determines that the status signal meets the predetermined signal criteria and a second state when the HID lamp status circuit determines that the status signal does not meet the predetermined signal criteria. When the control circuit is in the first state, the control circuit outputs a control signal for input into the switch circuit that configures the switch circuit into the first state. When the control circuit is in the second state, the control circuit outputs a control signal for input into the switch circuit that configures the switch circuit into the second state.
In a related aspect, the present invention is directed a ballast system, comprising a high-intensity discharge lamp, power feedback circuitry that provides a status signal that represents the state of energization of the high-intensity discharge lamp, an auxiliary light source, a voltage source for energizing the high-intensity discharge lamp and the auxiliary light source, a HID lamp status circuit having an input for receiving the status signal and determining whether the status signal meets the predetermined signal criteria, a switch circuit for controlling the application of the voltage source to the auxiliary light source wherein the switch circuit has a first state that effects application of the voltage source to the auxiliary light source, and a second state that isolates the voltage source from the auxiliary light source, and a control circuit responsive to the HID lamp status circuit for controlling the switch circuit. The control circuit has a first state when the HID lamp status circuit determines that the status signal meets the predetermined signal criteria and a second state when the HID lamp status circuit determines that the status signal does not meet the predetermined signal criteria. When the control voltage is in the first state, the control circuit outputs a control signal for input into the switch circuit that configures the switch circuit into the first state. When the control circuit is in the second state, the control circuit outputs a control signal for input into the switch circuit that configures the switch circuit into the second state.
In a further aspect, the present invention is directed to a method of operating an auxiliary lighting system for a high-intensity discharge lamp, comprising the steps of providing an auxiliary lighting system comprising an auxiliary light source, a HID lamp status circuit, and a switch circuit for controlling the application of a voltage source to the auxiliary light source, inputting into the HID lamp status circuit a status signal representative of the operational state of a high intensity discharge lamp, determining whether the status signal meets predetermined signal criteria, and controlling the switch circuit to apply a voltage source to the auxiliary light source if the status signal meets the predetermined signal criteria.
In yet a further aspect, the present invention is directed to a method of operating a ballast system comprising the steps of providing a ballast system comprising a high intensity discharge lamp, a voltage source for powering the high-intensity discharge lamp, circuitry for controlling the application of power to the high-intensity discharge lamp and providing a status signal that represents the operational state of the high-intensity discharge lamp, an auxiliary lighting system having an auxiliary light source, an HID lamp status circuit for determining whether the status signal meets predetermined signal criteria, a switch circuit for controlling the application of the voltage source to the auxiliary light source, and a control circuit for controlling the switch circuit. The method further comprises the steps of determining whether the status signal meets the predetermined signal criteria, controlling the switch circuit to apply the voltage source to the auxiliary light source if the status signal meets the predetermined signal criteria, and controlling the switch circuit to isolate the voltage source to the auxiliary light source if the status signal does not meet predetermined signal criteria.